Search Results (4,185)

To fabricate thermoelectric generators (TEGs) with high mechanical strength using single-walled carbon nanotubes (SWCNTs), we combined SWCNTs, poly(3, 4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS), and sodium alginate (SA) to synthesize flexible SWCNT/PEDOT:PSS/SA composite yarns via wet spinning. The composite yarns were flexible and dense, with a diameter of approximately 290 µm. Their tensile strength and breaking strain were 151 MPa and 12.7%, respectively, which were approximately 10 and 4 times those of the SWCNT films. However, the thermoelectric properties of the composite yarns were inferior to those of the SWCNT films. The temperature distribution and output voltage of the fabricated TEG with composite yarns were measured at a heater temperature of 100 °C. The temperature difference generated by the TEG with composite yarns was approximately 75% of that generated by the TEG with SWCNT films because the composite yarn had a smaller specific surface area. The output voltage of the TEG with two composite yarns (0.21 mV) was lower than that of the TEG with two SWCNT films. However, arranging the composite yarns at a high density resulted in an output voltage exceeding that for the TEGs with SWCNT films. These findings are highly beneficial for yarn-based TEGs used in wearable sensors. Full article

This study presents a comprehensive morphological and structural analysis of carbon materials produced via simple thermal methane pyrolysis conducted under laboratory conditions in a quartz reactor without the use of catalysts. The process, carried out at 1000 °C, achieved moderate methane conversion (36.5%), process efficiency (36.1%), and very high selectivity (98.9%) towards hydrogen production, highlighting its potential as a CO₂-free hydrogen generation method. Distinct carbon morphologies were observed depending on the formation areas within the reactor: a predominant flake-like silver carbon formed on reactor walls at temperatures between 600 and 980 °C (accounting for 91% of the solid product) and a minor powdery carbon formed near 980–1000 °C (9% of the solids). The powdery carbon exhibited a high specific surface area (125.3 m²/g), substantial mesoporosity (60%), and porous spherical aggregates, indicating an amorphous structure. In contrast, flake-like carbon demonstrated a low surface area (1.99 m²/g), high structural order confirmed by Raman spectroscopy, and superior thermal stability, making it suitable for advanced applications requiring mechanical robustness. Additionally, polycyclic aromatic hydrocarbons were detected in cooler zones of the reactor, suggesting side reactions in low-temperature areas. The study underscores the impact of temperature zones on carbon structure and properties, emphasizing the importance of precise thermal control to tailor carbon materials for diverse industrial applications while producing clean hydrogen. Full article

EPS module buildings are prefabricated, low-rise systems with high thermal insulation that are widely used in rural self-built houses in northern China, yet their indoor thermal environments often suffer from instability. This study experimentally verified the effectiveness of microcapsule phase change mortar (PCM plaster) in improving winter indoor temperatures of EPS module houses. In addition, based on simulation data from 350 design combinations across five representative cold-climate cities and four envelope design variables, the study provides quantitative design guidance for EPS module walls and PCM plaster in rural houses, offering a practical approach to improve indoor thermal stability that has not been previously reported. The main findings are as follows: (1) The thermal transmittance of EPS module walls is the dominant factor influencing indoor thermal performance. For climate adaptability, Type II walls are recommended for severely cold regions, while Type I walls are suitable for cold regions. The application of PCM plaster is not recommended in solar-rich cold regions such as Lhasa due to limited effectiveness. (2) Optimal PCM plaster parameters exist, with the phase change temperature recommended to be 2–4 °C higher than the average indoor operative temperature during the heating period. Specifically, 18 °C is optimal for Type I walls in Yinchuan, Beijing, and Dalian, while 15 °C is more appropriate for Type II walls in Shenyang and Harbin. The corresponding optimal thicknesses are 20 mm for Harbin, Shenyang, and Dalian; 30 mm for Yinchuan; and 40 mm for Beijing, achieving a balance between indoor temperature improvement and construction cost. (3) Operative temperature and discomfort hours are introduced to assess indoor thermal stability, especially in buildings with interior PCM plaster. Full article

In this numerical and experimental study, the effects of the width, length, and height parameters of a mirror arm on the drag coefficients of two side-view mirror models were investigated. The analyses were performed according to fractional factorial Taguchi L9 experiment plans. In the wind tunnel, a constant-temperature hot-wire anemometer and a pressure scanner system were used to measure velocity and static pressures, respectively. A realizable k-ε turbulence model with a scalable wall function was applied in the simulations, and the velocity was kept constant at 30 m/s. Means of the drag coefficient, signal/noise values, and analysis of variance were used to evaluate the parameters’ effects. The results showed that the drag coefficients increased with arm height. The increase in arm width decreased the drag coefficient to a limited extent, while the aspect ratio (width/height) showed a strong negative correlation with the drag coefficient. The high aspect ratios resulted in streamlined geometries around the mirror arm and delayed flow separations. The numerical analysis results showed good agreement with the experimental values for both mirror models. Full article

Conventional grain monitoring systems often rely on isolated data points (e.g., point-based temperature measurements), limiting holistic condition assessment. This study proposes a novel Mechanism and Data Driven (MDD) framework that integrates physical mechanisms with real-time sensor data. The framework quantitatively analyzes solar radiation and external air temperature effects on silo boundaries and introduces a novel interpolation-optimized model parameter initialization technique to enable comprehensive grain condition perception. Rigorous multidimensional validation confirms the method’s accuracy: The novel initialization technique achieved high precision, demonstrating only 1.89% error in Day-2 low-temperature zone predictions (27.02 m² measured vs. 26.52 m² simulated). Temperature fields were accurately reconstructed (≤0.5 °C deviation in YOZ planes), capturing spatiotemporal dynamics with ≤0.45 m² maximum low-temperature zone deviation. Cloud map comparisons showed superior simulation fidelity (SSIM > 0.97). Further analysis revealed a 22.97% reduction in total low-temperature zone area (XOZ plane), with Zone 1 (near south exterior wall) declining 27.64%, Zone 2 (center) 25.30%, and Zone 3 20.35%. For dynamic evolution patterns, high-temperature zones exhibit low moisture (<14%), while low-temperature zones retain elevated moisture (>14%). A strong positive correlation between temperature and relative humidity fields; temperature homogenization drives humidity uniformity. The framework enables holistic monitoring, providing actionable insights for smart ventilation control, condensation risk warnings, and mold prevention. It establishes a robust foundation for intelligent grain storage management, ultimately reducing post-harvest losses. Full article

Magnetohydrodynamic (MHD) flow and heat transfer in porous media are central to many engineering applications, including heat exchangers, MHD generators, and polymer processing. This study examines the boundary layer flow and thermal behavior of an electrically conducting viscous fluid over a porous stretching tube. The model accounts for nonlinear thermal radiation, internal heat generation/absorption, and Darcy–Forchheimer drag to capture porous medium resistance. Similarity transformations reduce the governing equations to a system of coupled nonlinear ordinary differential equations, which are solved numerically using the BVP4C technique with Response Surface Methodology (RSM) and sensitivity analysis. The effects of dimensionless parameters magnetic field strength (M), Reynolds number (Re), Darcy–Forchheimer parameter (Df), Brinkman number (Br), Prandtl number (Pr), nonlinear radiation parameter (Rd), wall-to-ambient temperature ratio (rw), and heat source/sink parameter (Q) are investigated. Results show that increasing M, Df, and Q suppresses velocity and enhances temperature due to Lorentz and porous drag effects. Higher Re raises pressure but reduces near-wall velocity, while rw, Rd, and internal heating intensify thermal layers. The entropy generation analysis highlights the competing roles of viscous, magnetic, and thermal irreversibility, while the Bejan number trends distinctly indicate which mechanism dominates under different parameter conditions. The RSM findings highlight that rw and Rd consistently reduce the Nusselt number (Nu), lowering thermal efficiency. These results provide practical guidance for optimizing energy efficiency and thermal management in MHD and porous media-based systems.: Full article

JP-10 (exo-tetrahydrodicyclopentadiene) is a high-energy-density hydrocarbon broadly used in advanced aerospace propulsion as a regenerative cooling fluid; in this study, we aimed to clarify how fuel pressure affects its thermal degradation (oxidative and pyrolytic) in near-isothermal flowing reactor. Experiments were performed under oxidative conditions (wall temperature 623.15 K, p = 0.708–6.816 MPa) and pyrolytic conditions (wall temperature 793.15 K, p = 2.706–7.165 MPa); carbon deposits were quantified by LECO analysis, oxidation activity was assessed by temperature-programmed oxidation (TPO), and morphology was performed by FESEM and EDS. Results show that oxidative coking is minimal (5.37–14.95 μg·cm²) and largely insensitive to pressure in the liquid phase (1.882–6.816 MPa), whereas at 0.708 MPa (gas/phase-change conditions), deposition increases, implicating phase and local heat-transfer effects. Under oxidative conditions, deposits are predominantly amorphous carbon with a disordered structure, formed at relatively low temperatures, with only a few fiber-like metal sulfides identified by EDS. In contrast, under pyrolysis conditions, the deposits are predominantly carbon nanotubes, exhibiting well-defined tubular morphology formed at elevated temperatures via metal-catalyzed growth. The pyrolysis coking yield is substantially higher (66.88–221.89 μg·cm⁻²) and increases with pressure. The findings imply that the pressure influences the coking of JP-10 via phase state under oxidative conditions and residence time under pyrolytic conditions, while basic morphologies of coke deposits remain similar; operationally, maintaining the working pressure higher than the saturated vapor pressure can mitigate oxidation coking associated with phase transitions, and minimizing residence time can mitigate pyrolytic coking. Full article

The subject of this paper is an analysis of the use of wall heating and cooling modules with heat pipes for efficient space heating and cooling. The modules under consideration constitute a structural element installed in the room’s partition structure and consist of heat pipes embedded in a several-centimeter layer of concrete. Water-based central heating and chilled water systems were used as the heat and cooling source. The heat pipes are filled with a thermodynamic medium that changes state in repeated gas–liquid cycles. The advantage of this solution is the use of heat pipes as a heating and cooling element built into the wall, instead of a traditional water system. This solution offers many operational benefits, such as reduced costs for pumping the heat medium. This paper presents an analysis of the potential of using heat pipe modules for heating and cooling in real-world buildings in Poland. Taking into account the structural characteristics of the rooms under consideration (i.e., internal wall area, window area), an analysis was conducted to determine the potential use of the modules for space heating and cooling. The analysis was based on rooms where, according to the authors, the largest possible use of internal and external wall surfaces is possible, such as hotels and schools. Based on the simulations and calculations, it can be concluded that the modules can be effectively used in Poland as a real heating and cooling element: standalone, covering the entire heating and cooling demand of a room, e.g., a hotel room, or as a component working with an additional system, e.g., air cooling and heating in school buildings. The changes in outdoor air temperature, during the year analyzed in the article, were in the range of −24/+32 °C. Full article

Electromagnetic Railguns Face Severe Ablation and Melting Risks Due to Extremely High Transient Thermal Loads During High-Speed Launching, Directly Impacting Launch Reliability and Service Life. To address this thermal management challenge, this study proposes and validates the effectiveness of spray cooling technology. Leveraging its high heat transfer coefficient, exceptional critical heat flux (CHF) carrying capacity, and strong transient cooling characteristics, it is particularly suitable for the unsteady thermal control during the initial launch phase. An experimental platform was established, and a three-dimensional numerical model was developed to systematically analyze the dynamic influence mechanisms of nozzle inlet pressure, flow rate, spray angle, and spray distance on cooling performance. Experimental results indicate that the system achieves maximum critical heat flux (CHF) and rail temperature drop at an inlet pressure of 0.5 MPa and a spray angle of 0°. Numerical simulations further reveal that a 45° spray cone angle simultaneously achieves the maximum temperature drop and optimal wall temperature uniformity. Key parameter sensitivity analysis demonstrates that while increasing spray distance leads to larger droplet diameters, the minimal droplet velocity decay combined with a significant increase in overall momentum markedly enhances convective heat transfer efficiency. Concurrently, increasing spray distance effectively improves rail surface temperature uniformity by optimizing the spatial distribution of droplet size and velocity. Full article

Water walls in power plant boilers are prone to failure under extreme conditions involving high temperature, corrosion, and wear, which severely threaten unit reliability and operational economy. In this work, a NiCr-Cr₃C₂ protective coating was deposited on SA213-T12 steel substrates using high-velocity oxy-fuel (HVOF) spraying, with arc-sprayed PS45 coating as a reference. The NiCr-Cr₃C₂ coating exhibited a dense, low-porosity structure with homogeneous dispersion of Cr₃C₂ hard phases in the NiCr matrix, forming a typical cauliflower-like composite morphology. During high-temperature sulfate corrosion tests at 750 °C, the NiCr-Cr₃C₂ coating demonstrated superior corrosion resistance, with a weight gain of only 2.7 mg/cm², significantly lower than that of the PS45 coating and the SA213-T12 substrate. The higher microhardness and lower friction coefficient also indicate excellent high-temperature wear resistance. The enhanced performance of the NiCr-Cr₃C₂ coating is attributed to the high Cr content, which promotes the formation of a continuous and protective scale composed of Cr₂O₃ and NiCr₂O₄, effectively inhibiting corrosive diffusion and penetration. This work demonstrates the application prospects of NiCr-Cr₃C₂ coatings on water walls of power plant boilers and guides the development of advanced HVOF coatings. Full article

Urban school environments often face significant thermal discomfort due to extensive paved surfaces, limited vegetation, and outdated building designs. This study examines how green spaces can mitigate temperature extremes and improve thermal comfort at two secondary schools in Coimbra, Portugal: Escola Secundária José Falcão (ESJF) and Escola Secundária D. Dinis (ESDD). Using a mixed-methods approach that combined school community surveys with on-site microclimatic measurements, we integrated user feedback on comfort with data on temperature and humidity variations across different indoor and outdoor spaces. Results revealed that tree-shaded areas consistently maintained lower air temperatures and higher relative humidity than unshaded zones, which experienced intense heat accumulation—up to a 5 °C difference. At ESJF, the older infrastructure and large asphalt surfaces led to severe heat retention, with east-facing classrooms recording the highest indoor temperatures. ESDD’s pavilion-style layout and existing green spaces provided comparatively better thermal conditions, although insufficient vegetation maintenance and limited shade reduced their effectiveness. The findings demonstrate a clear correspondence between the school community’s perceptions of thermal comfort and the measured microclimatic data. Vegetation—particularly deciduous trees—plays a critical role in cooling the school microclimate through shading and evapotranspiration. Strategic interventions such as expanding tree cover in high-exposure areas, installing green roofs and walls, and carefully selecting species can significantly reduce temperature extremes and improve outdoor usability. In addition, fostering environmental education and participatory co-design programs can encourage sustainable behaviors within the school community, underlining the importance of inclusive, nature-based solutions for climate adaptation. This research highlights that integrating green infrastructure in school design and management is a cost-effective strategy for thermal regulation. Green spaces, when co-designed with community involvement, not only enhance climate resilience and student well-being but also contribute to broader sustainable urban development goals. Full article

Hakka traditional vernacular dwellings embody regionally specific climatic adaptation strategies. This study takes the Meizhou Guangludi enclosed house as a case study to evaluate its climate adaptability with longevity and passive survivability factors of the Hakka three-hall enclosed house under subtropical climatic conditions. A mixed research method is employed, integrating visualized parametric modeling analysis and on-site measurement comparisons to quantify wind, temperature, solar radiation/illuminance, and humidity, along with human comfort zone limits and building environment. The results reveal that nature erosion in the Guangludi enclosed house is the most pronounced during winter and spring, particularly on exterior walls below 2.8 m. Key issues include bulging, spalling, molding, and fractured purlins caused by wind-driven rain, exacerbated by low wind speeds and limited solar exposure, especially at test spots like the E8–E10 and N1–N16 southeast and southern walls below 1.5 m. Fungal growth and plant intrusion are severe where surrounding trees and fengshui forests restrict wind flow and lighting. In terms of passive survivability, the Guangludi enclosed house has strong thermal insulation and buffering, aided by the Huatai mound; however, humidity and day illuminance deficiencies persist in the interstitial spaces between lateral rooms and the central hall. To address these issues, this study proposes strategies such as adding ventilation shafts and flexible partitions, optimizing patio dimensions and window-to-wall ratios, retaining the spatial layout and Fengshui pond to enhance wind airflow, and reinforcing the identified easily eroded spots with waterproofing, antimicrobial coatings, and extended eaves. Through parametric simulation and empirical validation, this study presents a climate-responsive retrofit framework that supports the sustainability and conservation of the subtropical Hakka enclosed house. Full article

Drug delivery is a well-established method for transporting anticancer drugs to cancerous tumors while minimizing damage to surrounding healthy tissues. Carbon nanocapsules (CNs) and boron nitride nanocapsules (BNNs) are promising nanocarriers capable of delivering drugs to tumor sites following their release. In this context, their diffusivity characteristics and drug release behavior need to be thoroughly addressed. This study examines the diffusion mechanisms of CNs and BNNs, as well as the impact of nanobubble cavitation on their performance as drug-releasing agents, utilizing molecular dynamics (MD) simulation methods. The results revealed that BNNs exhibit a higher diffusion coefficient compared to CNs in pure water. Moreover, temperature cannot be employed as a navigation mechanism for either CNs or BNNs. In terms of drug release, the collapse of nanobubbles at 298 K and 1 atm generates a high-energy water nanohammer, characterized by a temperature of approximately 1000 K and a pressure of 25 GPa, which impacts the nanocapsules. The impulse from the water nanohammer crushes the CN nanocapsule, whereas it leads to wall breakage in the BNN nanocapsule. Although both crushing and breakage can enable drug release, the crushing of CNs presents a higher risk of damage to the encapsulated drug. In summary, BNNs demonstrate better diffusivity and more favorable drug release behavior under nanobubble cavitation. However, further investigation is required to address targeting mechanisms and safer release strategies, involving the use of metallic functional groups and beam radiation, respectively. Full article

Vasconcellea pubescens (mountain papaya) is an underutilized Andean fruit with distinctive nutritional and functional properties, yet its rapid softening and short shelf-life result in significant postharvest losses. This review summarizes current knowledge on the physiology of fruit development and ripening, with emphasis on cell wall disassembly, color changes, and ethylene regulation as determinants of postharvest quality. Advances in postharvest management strategies, including temperature control, packaging, and ethylene-modulating treatments (such as 1-MCP), are discussed in the context of preserving fruit firmness, extending shelf life, and reducing food waste. Furthermore, the high content of bioactive compounds—such as papain, phenolics, and flavonoids—underscores the potential of valorizing by-products through sustainable biotechnological applications. Despite recent progress, critical gaps remain in genomic resources, predictive quality monitoring, and large-scale implementation of preservation techniques. Addressing these challenges could enhance the economic and ecological value of V. pubescens, positioning it as both a model species for postharvest research and a promising fruit for reducing food losses in horticultural supply chains. Full article

Effective thermal management of molds is a governing factor of the quality and stability of the injection molding process. This study introduces and validates an integrated cooling layer within a thin-walled insert mold designed to enhance thermal control and cavity filling performance. A coupled heat transfer simulation model was developed and subsequently calibrated against experimental temperature measurements. To isolate the mold’s intrinsic thermal response, temperatures were measured during distinct heating and cooling cycles, free from the perturbations of polymer melt flow. The validated mold was then installed on a Haitian MA1200 III injection molding machine to conduct molding trials under various injection pressures. A strong correlation was found between the simulation and experimental results, particularly as pressure increased, which significantly improved cavity filling and reduced the deviation between the two methods. The integrated cooling layer was shown to enhance heat dissipation, minimize thermal gradients, and promote a more uniform thermal field. This, in turn, improved filling stability, especially at moderate injection pressures. These findings provide robust quantitative data for simulation model calibration and mold design optimization, highlighting the potential of advanced cooling strategies to significantly enhance injection molding performance. Full article